N777PGPiper Aircraft PA 46-350P · 2010

On January 31, 2016, at 1459 Pacific standard time, a Piper PA46-310P, N777PG, performed a forced landing at Burns Municipal Airport, Burns, Oregon, following a total loss of engine power during cruise. The airplane was registered to and operated by the pilot as a 14 Code of Federal Regulations Part 91 personal flight. The private pilot, who was the sole occupant, was not injured, and the airplane sustained substantial damage during the landing roll. The cross-country flight departed Boeing Field/King County International Airport, Seattle, Washington, at 1318, with a planned destination of Scottsdale Airport, Scottsdale, Arizona. Visual meteorological conditions prevailed throughout the flight, and an instrument flight rules (IFR) flight plan had been filed.

The pilot reported that about 90 minutes after departure while cruising at 19,000 ft, the engine "tone" decreased, accompanied by a drop in manifold pressure from 29 to 15 inches. He kept the throttle in the cruise power position, and elected to divert towards Burns, after reporting to air traffic control personnel that he had an engine emergency. He stated that the engine did not regain power during the descent, and he did not perform any troubleshooting procedures. He eventually arrived over the airfield with altitude remaining, and began a circling descent. During the landing approach, he moved the gear selection lever to the DOWN position, but did not hear or feel any indication that the gear had deployed, nor did he see three green lights on the instrument panel indicating the gear was down and locked. He did not have time to perform the emergency extension procedure because the airplane was too low, and he decided to land gear-up on the snow adjacent to runway 30.

He reported that just prior to touchdown, when the airplane was about 5 ft above ground level, the landing gear began to extend, and he saw two green lights indicating the main landing gear had locked, but no green light for the nose gear. The airplane touched down, and the nose dug into the snow. The airplane abruptly stopped, sustaining substantial damage to the forward fuselage and both wings (Photo 1).

Photo 1 - Airplane at the Accident Site

The low-wing, high-performance, pressurized airplane was manufactured in 1987. It was equipped with a twin-turbocharged six-cylinder Continental TSIO-550-C14B engine, manufactured in November 2011. The engine had accrued 431.8 flight hours at the time of the last annual inspection, which was completed 18 days and 9.7 flight hours before the accident.

The aircraft was equipped with hydraulically operated, retractable, tricycle landing gear, with hydraulic pressure provided by an electrically driven hydraulic pump. Gear operation was controlled by a conventional two-position selector switch. Three green lights, which are individually activated as each gear mechanically locks into the down position are located above the landing gear selector.

The landing gear is held in the up position by hydraulic pressure which is trapped in the system lines by a check valve in the pump assembly.

The emergency gear extension system is activated by manually pulling a control on the instrument panel. The control activates a valve which relieves the pressure in the up side of the circuit, and bypasses fluid to the down side of the system. The additional fluid required for down operation comes directly from the reservoir. The landing gear is held in the down position by spring-loaded mechanical locking mechanisms built into the actuating cylinders of each landing gear leg.

The Pilot's Operating Handbook includes three initial steps for emergency procedures for an engine power loss in flight. The steps call for the pilot to switch fuel tanks, set the auxiliary fuel pump to LOW, and set induction air to ALTERNATE. If power is not restored, the axillary fuel pump should then be set to HIGH, fuel mixture FULL RICH, and the throttle to approximately 75 % power.

The low-wing, high-performance, pressurized airplane was manufactured in 1987. It was equipped with a twin-turbocharged six-cylinder Continental TSIO-550-C14B engine, manufactured in November 2011. The engine had accrued 431.8 flight hours at the time of the last annual inspection, which was completed 18 days and 9.7 flight hours before the accident.

The aircraft was equipped with hydraulically operated, retractable, tricycle landing gear, with hydraulic pressure provided by an electrically driven hydraulic pump. Gear operation was controlled by a conventional two-position selector switch. Three green lights, which are individually activated as each gear mechanically locks into the down position are located above the landing gear selector.

The landing gear is held in the up position by hydraulic pressure which is trapped in the system lines by a check valve in the pump assembly.

The emergency gear extension system is activated by manually pulling a control on the instrument panel. The control activates a valve which relieves the pressure in the up side of the circuit, and bypasses fluid to the down side of the system. The additional fluid required for down operation comes directly from the reservoir. The landing gear is held in the down position by spring-loaded mechanical locking mechanisms built into the actuating cylinders of each landing gear leg.

The Pilot's Operating Handbook includes three initial steps for emergency procedures for an engine power loss in flight. The steps call for the pilot to switch fuel tanks, set the auxiliary fuel pump to LOW, and set induction air to ALTERNATE. If power is not restored, the axillary fuel pump should then be set to HIGH, fuel mixture FULL RICH, and the throttle to approximately 75 % power.

The pilot made himself available for interview, but despite multiple requests, did not submit a Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2).

The pilot reported that during a flight in the accident airplane about 6 to 7 years prior, he had experienced a drop in manifold pressure during cruise, but on that occasion, had decided to continue the flight. After landing he discovered that the turbocharger crossover pipe had detached, and that this could have caused an in-flight fire. It was that prior experience that prompted him to initiate a rapid descent to land during the accident flight, rather than attempt to troubleshoot the loss of power.

The pilot further reported that a few years before the accident he had experienced two separate instances when the landing gear failed to extend after flying at high altitudes (FL22), in cold temperatures. On those occasions, he had attempted to utilize the landing gear to expedite the descent, and both times the landing gear failed to initially extend, but at some point, it eventually deployed as he got closer to the ground. He stated that he discussed the problem with multiple mechanics, with the consensus that this was not necessarily unusual, could likely be attributed to the cold temperatures, and that a thorough landing gear inspection should be performed if it persisted. It did not happen again, and he did not have the landing gear inspected.

Engine Monitor

The airplane was equipped with a JPI EDM-700 Engine Monitor. The unit was sent to the NTSB Office of Research and Engineering for data extraction. The EDM-700 recorded exhaust gas temperatures (EGT), cylinder head temperatures (CHT), turbine inlet temperature (TIT), and battery voltage from the time between engine start and the accident.

The extracted data revealed that the EGT and CHT values varied in concert with one another throughout the initial portions of the flight over a period which correlated to the takeoff and climb. At 1347, about 29 minutes after takeoff, the EGTs for all six cylinders reached about 1,500 degrees F, the CHT's about 290 degrees F, and TIT about 1,650 degrees F. The values remained closely matched and consistent for the next hour, until at 1448 an abrupt drop in EGT for all six cylinders to 150 degrees F, along with a similar drop in TIT was recorded. At the same time, CHT for all cylinders began gradually falling, reaching 80 degrees F, about 5 minutes later. At 1459, 11 minutes after the initial anomaly, the EGT displayed a momentary, 30-second increase from 150 to 300 degrees F along with a similar spike in TIT, the values then all dropped, and at 1501 the data ended. Battery voltage throughout the flight remained at 28 volts.

Airframe

The airframe sustained wrinkles aft of the firewall, with crush damage to the underside of the engine. Within the cabin, the fuel mixture control was found in the full-forward (RICH) position, the propeller was in the full-forward (INCR) position, and the throttle in the full-aft position (CLSD).

The auxiliary fuel pump switch was OFF, the fuel selector valve was in the LEFT position, both magneto switches were ON, and all circuit breakers appeared closed.

Both wings were removed from the airframe during recovery, and significant quantities of fuel were recovered from both fuel tanks at that time. During the examination, both the left and right collector/sump tanks were drained at their respective drain ports, and contained about 25 fluid ounces of clear blue-colored fuel each. Each tank also contained about 1 tablespoon of clear fluid, which was confirmed to be water when tested with water detecting paste.

The fuel filter bowl under the baggage compartment door was removed and contained about 5 fluid ounces of blue-colored fuel. The filter element was clear and free of debris, and no water was present.

The fuel line fittings from wing roots through to the engine driven fuel pump inlet were secure, and there were no indications of a leak. All fuel and vent lines were tested for blockage, and all were clear. The fuel selector valve was found in the left tank detent, and the valve could be moved freely between all positions.

Control continuity was established for the throttle, mixture, and propeller controls through to their respective control arms on the engine. All controls moved freely and in the correct direction.

Landing Gear

The nose landing gear remained stowed within the wheel well and appeared undamaged. Both main landing gear struts were in the fully extended and locked position; each wheel strut had bent aft and separated from the trunnion assembly.

The hydraulic system was intact, and no fluid leaks were observed. Power was applied to the airplane's electrical bus, and the hydraulic pump engaged and operated immediately. The landing gear system was examined, and no anomalies were noted which would have precluded normal operation.

During the last annual inspection, the landing gear emergency down spring, up-pressure switch, and sequence valve were replaced. The mechanic who performed the maintenance stated that the spring was an item that he typically replaces at every annual inspection, and that the sequencing valve was replaced because it was leaking hydraulic fluid at its actuating shaft. The pressure switch was operating intermittently, such that during the inspection the landing gear would not retract when commanded, unless the switch was tapped.

Engine

All fuel, oil, and induction lines appeared secure, and except for an indentation to the oil sump and right intercooler inlet manifold, no engine damage was observed beyond. The crankcase was intact, and there were no indications of catastrophic engine failure. The left and right magnetos remained firmly attached, and their engine timing was measured at 24 degrees, which corresponded to the specifications on the engine data tag.

The engine could be rotated by hand at the propeller flange, and cylinder compression was present when checked at the top spark plug bores of each cylinder.

The compressor impellers for both turbochargers could be rotated smoothly within their housings, and the inlet area of each compressor housing was undamaged.

The engine was removed from the airframe and shipped to the facilities of Continental Motors for testing. Once correctly configured within a test cell, the engine started on the first attempt, and was run at idle until operating temperatures were reached. The engine responded appropriately to a magneto check, and ran smoothly through speeds ranging from idle to 2,600 rpm and up to manifold pressures of 35.59 inHg.